The lenses and the total reflective block employed in the optical system of this invention are conventional and are used for their conventional purpose. Similarly, it is an established technique in optical systems to employ coaxial paths by training light on a target on one optical path and to split the reflections on that same optical path out from that path to a second or more optical paths. Prior art illustrating such path separation appears in the following published articles: IBM Technical Disclosure Bulletin, Vol. 16, No. 4, Sept. 1973, entitled "Mask to Wafer Alignment System", by R. Feder et al., at page 1307; and IBM Technical Disclosure Bulletin, Vol. 16, No. 5, Oct. 1973, entitled "Coupler for Optical Data", by L. Cooper, at pages 1470-1471; and IBM Technical Disclosure Bulletin, Vol. 22, No. 6, Nov. 1979, entitled "Optical Focusing Technique", by H. G. Nauth et al., at pages 2515-2516. No such art is known which includes an optical scanner with two coaxial paths having concentric lens systems.
Moreover, the more specific interrelationships of the design of this invention are not known to be closely similar to any prior art.